Web Inspector: Enable touch events feature fails touch feature detection

Web Inspector: Enable touch events feature fails touch feature detection
https://bugs.webkit.org/show_bug.cgi?id=84397

Source/WebCore:

Whenever the touch emulation is enabled, Inspector adds a script to evaluate on load,
that adds ontouch(start|end|move|cancel) properties to window.__proto__ and document.__proto__.

Reviewed by Pavel Feldman.

* inspector/front-end/DOMAgent.js:
(WebInspector.DOMAgent.prototype._emulateTouchEventsChanged.get if):
(WebInspector.DOMAgent.prototype._emulateTouchEventsChanged.scriptAddedCallback):
(WebInspector.DOMAgent.prototype._emulateTouchEventsChanged):
* inspector/front-end/inspector.js:

LayoutTests:

Reviewed by Pavel Feldman.

* fast/events/touch/emulate-touch-events-expected.txt:
* fast/events/touch/emulate-touch-events.html:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@115569 268f45cc-cd09-0410-ab3c-d52691b4dbfc